The alkylation of aromatic compounds with olefins and alcohols using acidic zeolites and homogeneous Friedel Crafts catalysts such as aluminum chloride and boron trifluoride is well known. In such cases, the alkylated products tend to be primarily meta and para substituted, with only low concentrations of ortho products. Aluminum and magnesium oxides are commonly used to provide selective ortho substitution [see, for example U.S. Pat. Nos. 3,075,832; 3,093,587; and 3,843,606]; these oxides are generally used as their phenol "esters", e.g. aluminum phenoxide, thereby giving rise to aluminum waste by products.
Alkylation of aromatic compounds is practiced commercially to produce a variety of useful products. For example, benzene is alkylated with ethylene to produce ethylbenzene, an intermediate in the production of styrene (see K. Weissermel and H. J. Arpe, "Industrial Organic Chemistry", English Trans., Verlag Chemie, N.Y., 1978 pp. 293-296). Benzene is also alkylated with propylene to produce cumene, an intermediate for production of phenol (id., pp. 299-300), or to produce 1,3- or 1,4-diisopropylbenzenes, intermediates for production of resorcinol or hydroquinone (pp. 317-318). Phenol is also alkylated with ketones to produce bisphenols such as Bisphenol A (id., p. 315), and with olefins to produce a variety of alkylphenols (id.); alkylation with alcohols, especially methanol, is used to produce cresols and xylenols (id. p. 316), with ortho cresol and 2,6-xylenol being produced with aluminum catalysis (id.). It is thus readily apparent that there is considerable commercial significance to aromatic alkyla tion processes.
U.S. Pat. No. 3,642,912 teaches titanium dioxide as a catalyst for the vapor phase alkylation of phenol with either methanol or ethanol to produe mixtures of alkylated products. In this patent, large amounts of oxygen alkylated products (e.g. methoxybenzene or anisole) as well as meta and para substituted alkyl benzenes were formed; the highest ratio of o cresol to non ortho selective products reported was 3/1, while typical ratios were much lower. The use of olefins, esters and ethers as alkyl donor compounds was not described.
U.S. Pat. No. 3,418,379 teaches gallium oxide as a catalyst for the reaction of phenol with olefins to produce product mixtures in which ortho alkylated products predominate over meta and para isomers. The catalysts were not very active, giving only 26% phenol conversion with 1-butene at 325.degree. C., and 39% conversion at 400.degree. C. after reaction times of 3 hours. The ratio of ortho/para substitution was 22 at 325.degree. C., but dropped to 1.2 at the higher conversion observed at 400.degree. C. More over, the ratio of 2,6 (ortho-ortho) to 2,4 (ortho- para) dibutylphenols produced with butylene and other olefins from C3 to C8 was only 2.1/1, indicating a loss of ortho selectivity at higher levels of alkylation.
U.S. Pat. No. 4,329,517 teaches iron-based catalysts for the vapor phase ortho alkylation of phenols with methanol to produce cresols and xylenols These catalysts contain as a secondary component, a variety of other metals, including gallium; ratios of iron to gallium are typically 54/1. These catalysts gave high selectivity to ortho-substituted products
In Wei Mu, J. M. Herrmann and P. Pichat, Catalysis Letters 3(1989) 73-84, titanium tetrachloride containing a gallium salt was burned in a flame to produce a product containing 0.74 atomic % gallium. The surface area of this oxide (50 m.sup.2 /g) was identical to that of the titanium dioxide prepared in the absence of the gallium, thus indicating that no "chemical mixing" of the oxides had occurred. The absence of "chemical mixing" was also indicated by the fact that in this example, the relative activity of the gallium-doped product for the photooxidation of cyclohexane decreased from 1.0 to 0.24 (ostensibly due to the surface of the titanium dioxide being partially coated with gallium oxide). This reference contains no teaching of such catalysts in alkylation reactions.
Japanese Patent J6 1263932 A 861121 8701; (Derwent 86-01 Wpl 87-003725/01 XRAM-C87-001603) describes compositions consisting of a Group VIII metal (Pt, Ru, Rh, Pd, Os or Ir) on a sulfated titanium dioxide or zirconium oxide which optionally contains a modifying element including aluminum, gallium, indium and thorium. These catalysts were claimed to be useful for xylene isomerizations. Alkylations were not described. In contrast, the catalysts of the present invention do not contain sulfur; we have found that the "chemical mixing" of gallium and titanium gives an active alkylation catalyst and that sulfating is not necessary. Furthermore, a Group VIII metal is not necessary to perform alkylation reactions.
Gallium-containing catalysts having no titanium component are well-known for applications other than alkylation of aromatics For example, gallium has been found to be a useful modifier in zeolites used for the aromatization of alkanes (e.g. ethane-hexane conversion to benzene, toluene and xylenes); this is an upgrading of low-octane fuels to higher octane products. See: G. L. Price and Vladislav Kanazirev, J. Mol Catalysis 66(1991) 115-120; J. Kanai and N. Kawata, Applied Catalysis 62(1990) 141-150, and references cited therein.
Magnesium oxide catalysts containing titanium, uranium or chromium have been claimed as catalysts for the ortho-alkylation of phenols [see U.S. Pat. No. 4,283,574]. The ortho-directing selectivity is consistent with the fact that the catalyst contains magnesium as a major component.
As described below, we have found that insoluble, chemically-mixed oxides of titanium and gallium function as highly active catalysts for the alkylation of aromatic compounds, including phenols. These catalysts provide high levels of ortho substitution and do not produce the undesirable aluminum or magnesium wastes.